Fig. 2

Time course of the effects of insulin stimulation on GLUT4 subcellular localization and on glucose transport

Adipocytes were sampled before insulin addition at the indicated time points after the addition of 5 nM insulin. Subcellular fractions were isolated as in Fig. 1 and the amount of GLUT4 determined after SDS-PAGE and immunoblotting. Quantitative evaluation of immunoblots was done by densitometric scanning (Pharmacia-LKB Ultroscan) of films and integration of areas under peaks. Glucose transport was determined as 2-deoxy-D-[l-³H]glucose uptake, (a) Results of GLUT4 quantitation mean ± SEM (n = 3–12 separate experiments) and for glucose uptake (mean ± SEM, n = 3 separate experiments) are expressed as a percentage of nonstimulated controls (error bar is shown only where this value is greater than the graph symbol), (b) Data replotted as a percentage of the respective maximal (20 min) value. ●, Plasma membranes; ◯, caveolae; ◼, microsomal fraction; ▲, glucose transport.